Sealing tightness testing device

ABSTRACT

A sealing tightness measuring device and a pressure-retaining capability measuring gauge for a pressure container or system is provided. A pressure is produced against the testing fluid inside a piston cylinder communicated with the tested container or system by an assembly including a weight, a piston, and a piston cylinder successively arranged through a coaxial plumb bob. An equation RL=pt/C is used to represent the sealing tightness of the pressure container or system. The equation pt=p(p−0.5Δp)Δt/Δp is used in the pressure-retaining capability measuring gauge to express the pressure-retaining capability, wherein p is the fixed testing fluid pressure, t is the elapsed time for the fluid to leak completely, C is the volume of the pressure container or system, Δp is the drop value of the pressure, and Δt is the elapsed time for the pressure to descend from p to (p−Δp) caused by the leakage.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the national phase entry of International Application PCT/CN2016/091715, filed on Jul. 26, 2016, which is based upon and claims priority to Chinese Patent Application No. 201510561088.9, filed on Aug. 28, 2015, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to the technical field of fluid power transportation and fluid medium transportation systems, and further relates to the tightness test of the pressure containers or systems. Particularly, the present invention relates to a sealing tightness testing device i.e. a leakage resistance measuring device discovered and defined by the inventor and a pressure-retaining capability measuring gauge, which is also called as pressure-retaining gauge for short, discovered and defined by the inventor.

BACKGROUND

The unit of pressure Pa=N/m²=N·m/m³=energy storage of per unit volume of fluid i.e. the fluid energy storage of static pressure container E=pC, wherein p=pressure of the container, C=volume of the container. Therefore, if the time for all fluid to leak out from the container at a constant pressure p is t, with reference to the electrical current, let fluid leakage current I_(L)=C/t=fluid volume passing through the sealing section in per unit time (i.e. C=t I_(L)). With reference to the electrical resistance, let the leakage resistance R_(L)=p/I_(L)=the ratio of pressure to fluid leakage current. Based on the equation pC=pt I_(L), it can be known that pC/I_(L)=pt→CR_(L)=pt or R_(L)=pt/C=p/I_(L). Apparently, the value of pt is also referred as an inherent pressure-retaining property or the pressure-retaining capability of a pressure container or system. Since the greater the leakage resistance of the pressure container or system, the tighter is the sealing, there is no doubt that the leakage resistance refers to the tightness of the sealing. Moreover, according to R_(L)=pt/C, the tightness i.e. the leakage resistance can be understood as the pressure-retaining capability required to make the pressure container or system leak a unit volume of fluid. According to R_(L)=p/I_(L), the tightness i.e. the leakage resistance can be understood as the pressure (energy) required to make the pressure container or system leak a unit fluid current (i.e. leak a unit volume of fluid in per unit time). Therefore, CR_(L)=pt is the pressure-retaining (leakage) equation of a pressure container or system. This pressure-retaining or (leakage) equation is firstly discovered by the inventor of the present invention.

Since the volume and leakage resistance of any normal pressure container or system have constant value, the following can be derived based on the leakage equation CR_(L)=pt.

1) The pressure-retaining capability pt of any pressure container or system equals to the product of volume and leakage resistance thereof which is a constant. Just as explained by the instructions “the greater the volume and leakage resistance, the longer is the time required for complete leakage under a constant pressure; the higher the pressure, the shorter is the time required for the complete leakage under a constant pressure, and vice versa.”

2) The fluid leakage current is directly proportional to the pressure in any pressure container or system, and the ratio is the constant leakage resistance thereof, that is, the leakage resistance R_(L)=p/I_(L)=pt/C=a constant which shows that the leakage equation completely corresponds to the Ohm's law.

3) The unit of leakage resistance may be MPa·h·m⁻³. The unit of leakage rate i.e. the leakage derivative which equals to the reciprocal of leakage resistance may be m³·(MPa·h)⁻¹.

That is to say, the leakage equation is in full compliance with the objective laws of pressure-retaining and leakage of a pressure container or system, which is beyond doubt.

The fluid flowing through the sealing section inside the tube and on the surface of an object are all considered as the flows of fluid. The biggest difference is that the type and strength of the resistance that prevents fluid from flowing are different. Since there exists a leakage resistance corresponding to the energy-consuming electrical resistance, there should be a fluid reactance corresponding to the electrical reactance which does not consume energy, and the fluid impedance corresponding to the electrical impedance should also exist.

According to comparison, the electron flow with small mass is a motion of electrified bodies whose kinetic energy is negligible. Whereas, the molecular flow with great mass is a motion of unelectrified bodies whose kinetic energy is nonnegligible. Therefore, the stagnation and flow of electrons in the circuit perform as the conversion between voltage and current. Similarly, the stagnation and flow of molecules in the fluid circuit should be performed as the conversion between the pressure energy and kinetic energy of the fluid circuit. Since the electrical reactance is the conversion element which results the conversion of the voltage between two ends and the current therein, the fluid reactance should be the conversion element which results the conversion between the fluid pressure (energy) between two ends and the fluid kinetic energy therein.

Beyond all doubts, theoretically, the kinetic energy of the fluid is the result of the fluid pressure working on the stationary fluid, i.e. the kinetic energy of the fluid is 0.5 mv²=pAl→0.5ρv²=p, wherein m=the mass of the fluid, v=velocity of the fluid, ρ=m/(Al)=density of the fluid, and p=the pressure when doing work to stationary fluid (i.e. the pressure for giving kinetic energy to the fluid and no longer exist in the fluid with said velocity), l=the distance that a fluid cross-sectional surface with area of A moves under the action of force pA. Therefore, a conversion from pressure to kinetic energy exists during the transition of fluid from stationary state to flowing state and a conversion from kinetic energy to pressure exist during the transition of fluid from flowing state to stationary state. In the flowages where the flux and the velocity change constantly, constant conversions between pressure and kinetic energy exist. Moreover, the amount of pressure reduction (increase) in per unit volume of fluid Δp=the amount of kinetic energy increase (reduction) 0.5ρΔv².

Since the unit of the flow velocity of the fluid v is [m/s]=[(m³/m²)/s], the flow velocity of fluid v=the volume of the fluid flowing through the unit cross-sectional area in per unit time. Therefore the fluid flow rate (amount) of the volume of the fluid flowing through the cross-sectional area (A) in per unit time is defined as I_(F)=Av, which can also be understood as the volume of the fluid that can flow through the cross-sectional area A, when the fluid moves at velocity v for a unit of time.

Accordingly the kinetic energy of a unit volume of fluid 0.5ρv²=the pressure p for providing kinetic energy to the fluid, it can be known that,

$\begin{matrix} {p = {\rho \; {v^{2}/2}\mspace{14mu} \left( {{where},{\rho = {{fluid}\mspace{14mu} {density}}},{v = {{flow}\mspace{14mu} {velocity}\mspace{14mu} {of}\mspace{14mu} {fluid}}}} \right)}} \\ {= {\rho \; {{Av}^{2}/2}\; A\mspace{14mu} \left( {{where},{A = {{cross}\text{-}{sectional}\mspace{14mu} {area}\mspace{14mu} {of}\mspace{14mu} {fluid}\mspace{14mu} {current}}}} \right)}} \\ {= {\rho \; I_{F}{v/2}\; A\mspace{14mu} \left( {{where},{I_{F} = {{{fluid}\mspace{14mu} {current}} = {Av}}}} \right)}} \\ {= {I_{F}X_{F}\mspace{14mu} \left( {{where},{X_{F} = {{\rho \; {A/2}\; A} = {\rho \; {I_{F}/2}\; A^{2}}}}} \right)}} \end{matrix}$

Since the unit of X_(F)=p/I_(F) can be the same as the unit MPa·h·m⁻³ of leakage resistance and X_(F) is a factor of the conversion from pressure (energy) of the fluid to kinetic energy caused without energy consumption, with reference to electrical reactance, X_(F) should be named as fluid reactance of the fluid circuit, and I_(F) X_(F) should be named as the pressure drop caused by the fluid reactance.

Since the fluid reactance X_(F)=(ρv)/(2A) of a tube changes according to the cross-sectional area A of the tube cavity, the pressure drop I_(F)X_(F) (equals to the increase of kinetic energy caused by the pressure drop) caused by the fluid reactance of the tube is suddenly changed as the sudden change of the cross-sectional area A of the tube cavity along the flowing direction. In other words, the conversion from pressure to the kinetic energy caused by the fluid reactance is completed instantly, or the conversion from the pressure to kinetic energy results from the instant impact of the pressure to the fluid caused by the fluid reactance, or once the fluid flows, the impact pressure which causes the fluid to flow has been swallowed by the fluid. Since a pressure for overcoming frictional drag is further required for the flow of fluid, two component forces are always required when the fluid is flowing in the tubes, one is the pressure that allows the fluid to flow (I_(F) X_(F)), the other is the pressure that overcomes the frictional drag (I F R F). That is to say, the total pressure drop of the fluid flowing through the tube is p=I_(F) R_(F)+I_(F) X_(F)=I_(F) (R_(F)+X_(F)), wherein I_(F) X_(F) is the pressure loss caused by fluid resistance, I_(F) X_(F) is the pressure that the fluid resistance causes the fluid to swallow, or it can be understood that the tube is a series fluid circuit consisting of a fluid resistance R_(F) and a fluid reactance X_(F), and p=I_(F) (R_(F)+X_(F)) can be named as the flowing equation of fluid in the tube.

Actually, less or more, there exists a frictional drag between the contact surfaces of any two objects that have relative motion or relative motion trend to prevent them from moving relatively. Apparently, the frictional drag that the tube generates for the fluid flowing through the tube acts on the outer periphery of the fluid current. Poiseuille, a French physicist and biologist, proved that the frictional resistance of the tube against the fluid R_(F)=(8ηl)/(πr 4) (where, η=viscosity, 1=length of the tube, r=diameter of tube wall) by ultrafine tube in 1838. Not only the unit of the frictional resistance is not Newton, but also the frictional resistance equals to the ratio of the pressure p between two ends of the tube to the fluid current I_(F), which is the fluid resistance corresponding to the electrical resistance. Afterwards, people named the discovery as Poiseuille's law which is successfully applied in the field of fluid flowing with extremely low flow velocity, such as the human hypertension therapy and fluid viscosity measurement. Since people had no idea of the fluid reactance in the tube which causes pressure drop, people mistakenly believed that the reason why the Poiseuille's law only meets the fluid flowing in capillary tube but not the fluid flowing in normal tube is that there is an uncertainty pressure drop caused by the turbulent flow in the normal tube. Therefore, until now, the physical parameters of the fluid resistance are not defined and applied according to the Poiseuille's law.

Compared with the outer peripheral frictional drag against the fluid in the tube, the fluid reactance of the tube changing suddenly along with the fluid cross-sectional area is the frontal resistance from the diameter changing section or port of tube against the fluid. All of the resistance against the fluid passing through the sealing section, the outer peripheral resistance and front resistance against the fluid passing through the tube are the resistances against the fluid flowing through the fluid circuit, so they obviously have the same dimension. Therefore, since the unit of the outer peripheral frictional resistance against the fluid in tube defined according to the Poiseuille's law is MPa·h·m⁻³, it is obviously proved that Poiseuille's law and the fluid leakage equation and fluid current equation discovered by the inventor which reach the same goal by different means are scientific.

The wall-bulged passage of tube and moving object which are adjacent, have equivalent right (angle) inclusion volume and are coaxially formed by sharing a common generatrix [See XU Chang-Xiang, ZHANG Xiao-Zhong, CHEN You-Jun. Pressure Energy, Leak Resistance, Fluid Resistance and Fluid Reactance of Fluid. Hydrodynamic Pneumatics and Seals, 2015, 35 (9)] moving relative to the fluid at the same velocity for per body segment would cause the fluid whose volume equals to the right inclusion volume to be squeezed through the same solid surface and static-pressure fluid, or cause the same fluid to flow through the internal and external fluid circuit having the same fluid resistance and fluid reactance. Thus, it is apparent that the flow of the fluid flowing outside the moving object can be described according to the flowing equation of the fluid within the tube.

In conclusion, all flows of fluid can be described by the equation p=I_(F) (R_(F)+X_(F)), wherein p is the total pressure required for the flow of fluid, I_(F) is the fluid current, and R_(F) is the periphery or tangential resistance against the fluid current flowing through the flow-guiding surface (be called as fluid resistance against the fluid caused by conductor), X_(F) is the frontal or axial resistance against the fluid current flowing through the flow-blocking surface (be called as fluid reactance against the fluid caused by blocking body). The fluid reactance of the current-facing surface (port) or the diameter-shrinking section (port) is the positive fluid reactance that causes the conversion from pressure energy to kinetic energy. The fluid reactance of the back-to-current surface (port) or the diameter-expanding section (port) is the negative fluid reactance that causes the conversion from kinetic energy to pressure energy. I_(F)R_(F) is the irreversible pressure component caused by the fluid resistance. I_(F)X_(F) is the reversible pressure component of conversion between pressure energy and kinetic energy caused by the fluid reactance. The flows of fluid flowing through the sealing section and the capillary tube are flows having extremely low flow velocity or small flux, so the flows can be regarded as having fluid resistance without fluid reactance. The flows of fluid flowing through the diameter-changing tube section or port are the flows having extremely short flow distance, so the flows can be regarded as having fluid reactance without fluid resistance. The flows of fluid flowing through the tube section having uniform diameter can be regarded as having fluid resistance without fluid reactance. The flows of fluid flowing through normal pipelines can be regarded as having both fluid resistance and fluid reactance. Therefore, without knowing the fluid resistance, fluid reactance, fluid impedance and fluid flowing equations of the fluid circuit, it is impossible to realize an effective control to the flow and leakage of fluid and have a safe and reliable fluid power and medium transportation system. That is to say, the existing hydromechanics and the existing leakage-control IOS standard without knowing the effects of the fluid resistance (leakage resistance), fluid reactance and flow impedance on the flow of fluid deviate from the science and are the reason of many accidents.

It is not hard to observe that any flowing fluid that has a path to flow can always bypass or avoid the unshakeable frontal obstacle that the fluid current encounters in acceleration ways, while all the moving solid objects desperately impact the front obstacles that the objects encounter. These are the unique moving characteristics that fluid and solid respectively has. Since the static pressure of fluid is the only motive force that maintains a steady flow of fluid, when a fluid with no constant shape encounters a frontal obstacle, it is natural that the fluid would face a converging attack of the static pressure and the frontal resistance to speed up and cross flow, i.e. the behavior that the fluid accelerates to avoid the frontal obstacle. As described earlier, such phenomenon results from the pressure that instantly impacts the fluid caused by the fluid resistance or frontal resistance of the fluid. This is the mechanism by which the pressure of fluid decreases while the flow velocity increases. Therefore, the fact that existing hydromechanics having no idea of the phenomenon of “the pressure of fluid decreases while the flow velocity increases” (Bernoulli's principle) is enough to show that the existing hydromechanics has not yet touched on the substance of how the fluid flows, and how to effectively use and control the flow of fluid. Without these bases, how can we know the means to ensure the safety of the fluid dynamic and medium transportation?

The fluid reactance determines whether the fluid flows in acceleration or deceleration, i.e. determines how the fluid flows. However, to recognize the fluid reactance, based on the derivation process of fluid reactance described above, the leakage resistance or fluid resistance of fluid must be recognized first. Therefore, the discovery or definition of leakage resistance or fluid resistance of fluid is a necessary prerequisite for the discovery of fluid resistance. Originally, the leakage resistance of the fluid R_(L)=p/I_(L), corresponding to the electrical leakage resistance refers to the pressure required to leak a unit volume of fluid in per unit time. The fluid leakage rate 1/R_(L)=I_(L)/p corresponding to the electrical leakage rate i.e. the reciprocal of the electrical leakage resistance refers to the leakage amount of fluid volume caused by unit pressure, wherein I_(L)=leakage current of fluid=leakage volume of fluid in per unit time≠leakage volume of decompression fluid in per unit time, p=fluid pressure at leakage. However, ISO 5208, “Pressure Testing of Industrial Metallic Valves” (GB/T 13927) has incorrectly defined the leakage current (I_(L)) as the leakage rate and uses the leakage current to check the sealing, which is tantamount to use reciprocal 1/I_(L) of leakage current (I_(L)) as the standard of tightness i.e. leakage resistance to check the sealing, and is also tantamount to identify the constant WI, by the variable 1/I_(L). ISO 19879 “Testing Method for Fluid Dynamic Transportation Pipe Joints” (GB/T 26143) outlines that a sealing without visible leakage in a limited pressure-retaining time is an eligible sealing, which is tantamount to stipulate that a sealing with a visible leakage outside the limited pressure-retaining time is an eligible sealing. In fact, the standard still uses the volume of visible decompression fluid that leaks out of the pressure container in per (specifically defined) unit of time to check the sealing. That is substantially the same as ISO 5208, which still identify the constant p/I_(L), by the variable 1/I_(L). Although ISO 5208 and ISO 19879 identify the constant p/I_(L), by the variable 1/I_(L) without considering the condition where the leakage current changes along with the pressure, the sealing is identified by the leakage current under a certain pressure in a certain period of time. However, ISO/TR 11340 “Hydraulic Hose Assemblies Hydraulic Systems External Leakage Classification” (GB/Z 18427) classifies leakage into six levels according to the size of visible leakage current completely, regardless of the value of pressure. Due to the difficulty of collecting and measuring leakage fluid, in order to identify the quality of the sealing by naked eyes, ISO 5208 outlines specific conversion regulations between the mm³ volume of leakage in per second and the number of leakage drops and bubbles in per minute. When identifying the leakage of sealing by naked eyes, firstly the adhesivity and volatility of liquid and the negative-deviation testing pressure both may result in no leakage drop exists within the pressure duration; the observation of water depth and negative-deviation testing pressure of the bubbles may get the result that no bubble exists within the pressure duration; then the standard for judging whether the pressure container meets the requirements of no visible leakage is too low, which may cause the products with poor quality to get into the marketing line while the user cannot monitor and timely discover the leakage in the gas pipeline and narrow space, and in the underground and long-distance gas-liquid pipeline; eventually the leakage may inevitably be out of effective control, completely. So to speak, these standards fully prove that the existing sealing technology not only lacks scientific understanding of the sealing tightness i.e. leakage resistance, but also lacks scientific understanding and measurement means for the misused physical quantity (leakage current). That is to say, the existing sealing technology not only has no idea about that the leakage current is directly proportional to the testing pressure, but also has no idea about the differences between the volume occupied by the leaked compressed fluid and the volume of leaked decompression fluid. Moreover, the existing sealing technology has no idea about the error caused by the loss of adhesion and volatility of the leaked fluid. Even worse, the existing sealing technology requires to measure the meaningless leakage current knowing that the sealing has obvious leakage. Such requirement shows that the existing sealing technology not only does not have any scientific identification method and means for visible leakage, but also does not have any scientific identification method and means for invisible leakage. Therefore, the existing technical standards related to the sealing not only make the leakage of a pressure container or system completely out of control, but also contribute to the ignorance of how the fluid flows in the field of hydromechanics in a long period of time, which inevitably causes tremendous accidents in fluid power and medium transportation systems.

SUMMARY OF THE INVENTION

The objective of the present invention is to provide a testing device according to the sealing tightness (i.e. the leakage resistance) and the pressure-retaining capability discovered and defined by the inventor, and at least to turn people from unscientifically identifying visible leakage in the leakage detection of the pressure container and system into scientifically identifying the visible and invisible leakage, so as to make the uncontrollable leakages of pressure container and system become fully controllable by people.

Since the leakage resistance of the pressure container or system is greater, the sealing is tighter, the sealing tightness is the leakage resistance. The inventor has proved that the volume of fluid leaked from a pressure container or system in per unit time i.e. leakage current I_(L) is directly proportional to the fluid pressure p, and the ratio is the sealing tightness i.e. the leakage resistance R_(L), that is to say, the leakage resistance of a pressure container or system R_(L)=p/I_(L) which is a constant irrespective of the pressure p and the leakage current I_(L). However, in the prior art, the volume of decompression fluid leaked outside the container or system in per unit time i.e. the leakage current I_(L) is incorrectly called as the leakage rate and used to identify whether the sealing is good or not, which is at least tantamount to use a variable (proportionally changing along with the pressure p) (i.e. leakage current I_(L)) to identify a constant (the ratio of leakage current to pressure). This action is worthless. In order to change the situation where the quality of the sealing cannot be scientifically identified due to the unscientific definition of sealing tightness i.e. leakage resistance in the prior art, a sealing tightness i.e. leakage resistance testing device for pressure container or system is provided according to the sealing tightness i.e. the leakage resistance discovered and defined by the inventor (see FIGS. 1-3). The sealing tightness i.e. the leakage resistance discovered and defined by the inventor has the following characteristics, i.e. the leakage resistance R_(L)=p/I_(L)=pΔt/ΔC, p is a fixed testing fluid pressure of a pressure container or system; I_(L)=ΔC/Δt is the volume of the testing fluid leaked from the pressure container or system in per unit time; the fixed testing fluid pressure p is produced against the testing fluid inside the piston cylinder communicated with the tested container or system by an assembly in which a weight (06), a piston (05), and a piston cylinder (04) are successively arranged through a coaxial plumb bob; a ratio of the total gravity G of the assembly of the weight and the piston to a cross-sectional area A of the piston cylinder G/A is the fixed testing fluid pressure p; a product hA of a drop height h of the weight and piston descending along with the leakage and the cross-sectional area A of the piston cylinder is a volume of leaked testing fluid ΔC; Δt is the elapsed time for the volume of fluid ΔC to leak.

The leakage resistance R_(L)=pΔt/ΔC is determined by three variables i.e. the testing pressure p, the volume of leaked fluid ΔC, and the elapsed time Δt for leaking the volume of fluid ΔC. The testing pressure p is the ratio of the gravity G of the applied weight to the cross-sectional area A of the piston cylinder G/A. The ΔC is the product of the drop height h of the piston descending along with the leakage and the cross-sectional area A of the piston cylinder hA. Therefore, to get the original leakage resistance testing device, first, the fixed testing fluid pressure generating assembly should be placed or fixed on a horizontal operating platform (01) of a digital display height gauge through a piston cylinder seat (03 b). Then, the digital display height gauge is used to measure and display the drop height h of the weight and piston descending along with the leakage. A separate timer is used to record the elapsed time Δt for the piston to descent by the height h. After the leakage reaches the specified value of h or Δt and the value of Δt or h is read, the leakage volume ΔC=hA and the leakage resistance R_(L)=pΔt/ΔC are successively calculated according to the specified value of h or Δt, the read value of Δt or h and the known value A and p.

If the chip or microprocessor of the digital display height gauge in the original leakage testing device is substituted by a microprocessor that has the functions described below such as data input, acquisition, calculation and display and/or print output, then a program-controlled detector for leakage resistance may be acquired,

-   -   an input acquisition function for gravity G of the weight and         the cross-sectional area A of the piston cylinder;     -   a selection and input acquisition function for the drop height h         and the time Δt of the piston which are used as specific values;     -   an acquisition function for the drop height h and time Δt of the         piston that is synchronously cleared and started by a switch or         button;     -   a calculation function for calculating the testing pressure         p=G/A, the leakage volume ΔC=hA and the leakage resistance         R_(L)=pΔt/ΔC when the leakage reaches the specified value of h         or Δt; and     -   a function for at least outputting, displaying and/or printing         the value of leakage resistance R_(L).

Therefore, the characteristics of an improved leakage resistance testing device of the original device are as follows, i.e. the fixed testing fluid pressure generating assembly is placed or fixed on a horizontal operating platform (01) of a program-controlled detector, which can automatically calculate and at least display or/and print the leakage resistance after automatically collecting the calculation parameters ΔC and Δt of the leakage resistance, through a piston cylinder seat (03 b). Each test is performed under a specified or selected value of p until the leakage reaches a specified or selected value of ΔC or Δt.

The leakage resistance measurement of some pressure containers can be performed while the pressure container is directly placed on the horizontal operating platform (01) of the digital display height gauge or leakage resistance program-controlled detector. Under this situation, the piston cylinder (04) of testing fluid pressure generating assembly needs to be directly connected to the pressure container to be tested. However, some pressure containers and systems cannot be placed on the horizontal operating platform (01) for leakage resistance measurement. A piston cylinder seat (03 b) which allows a piston cylinder (04) to communicate with a hose assembly (03 a) should be placed on the horizontal operating platform (01) so as to conduct the testing pressure to the tested pressure container or system through the hose. In order to satisfy the requirements of these two situations at the same time, generally, the piston cylinder (04) and the piston cylinder seat (03 b) are separately manufactured. Obviously, the piston cylinder (04) and the piston cylinder seat (03 b) can be integrally manufactured, as long as the testing requirements for the pressure container and system placed outside the horizontal operating platform (01) are satisfied.

Since the operation of the leakage resistance testing device is complicated, it is merely applicable to the leakage resistance test of the seal-pressure container and system in finalized design while not applicable to the factory acceptance and operation monitoring of the finally designed pressure container and system. Since the volume C and the leakage resistance R_(L) of the finally designed pressure container and system are known or fixed, according to the leakage equation CR_(L)=pt, it can be known that whether the pressure-retaining capability value pt is qualified or merely whether there is any change of the pressure-retaining capability value pt needs to be checked for the factory acceptance and operation monitoring of the sealing of the finally designed pressure container and system pressure-retaining capability.

The leakage of any static-pressure container or system would cause a drop of pressure. Since the leakage that causes the pressure to drop from p to (p−Δp) is equivalent to a leakage in which a sub-space having a volume that is Δp/p times of the total volume is completely leaked under a pressure (p−0.5Δp). Therefore, if the elapsed time for the pressure p to drop by Δp is Δt, then the elapsed time for the complete leakage of the entire static-pressure container or system having p/Δp subspaces in total under the pressure p is (p/Δp)Δt, or the pressure-retaining capability of the entire static-pressure container or system is pt=(p/Δp) (p−0.5Δp)Δt. Obviously, the value of p/Δp is higher, the observation time is shorter, the test is closer to the constant-temperature and constant-pressure test, so the test is more accurate, and it is more proper to replace (p−0.5Δp) by p. This is the sealing theorem discovered by the inventor. According to this theorem, as long as the elapsed time Δt for the pressure of the static-pressure container and system leaking at any pressure p to drop by Δp is known, the pressure-retaining capability pt of the same can be known, even the leakage resistance R_(L)=pt/C can be known.

All the digital pressure gauges with range of tens or even hundreds of megapascals (MPa) in the prior art can resolve pressure changes of 0.001 MPa. Therefore, once the acquisition circuit of the elapsed time Δt for the pressure to change Δp and the calculation circuit of the pressure-retaining capability pt=p(p−0.5Δp)Δt/Δp are added to the pressure acquisition and identification chip of the digital pressure gauges in the prior art, it can be used to detect the pressure-retaining capability of any pressure container and system under any pressure. Therefore, a measurement gauge of pressure-retaining capability pt of a pressure container or system is provided, and the measurement gauge has the following characteristics i.e. pt=p(p−0.5Δp) Δt/Δp, wherein t is the elapsed time for a complete leakage of fluid inside a pressure container or system under a fixed pressure p; Δt is the elapsed time for the pressure of the pressure container or system to drop from p to (p−Δp) due to leakage; pt is automatically calculated and displayed after p, Δp, and Δt are automatically collected; and each test is performed until the specified or selected value of Δp or Δt is reached by the leakage.

If two ends of long-distance pipeline or system having uniform diameter are each installed with a pressure-retaining capability gauge, and the two ends of the segment of the pipeline or system are disconnected or the pressure source is removed under a working pressure to perform the pressure-retaining capability test, when the displayed pressure-retaining capability value pt of two gauges are equal to each other and is not less than a due value, it is supposed that the sealing did not change, when the displayed pressure-retaining capability value pt of two gauges are not equal to each other, it is supposed that there is a centralized leaking point which is closer to the gauge with lower value because the tested pipeline is a static-pressure pipeline and no fluid reactance but merely fluid resistance which is 0.5 times of the leakage current exists. According to Poiseuille's law, the leakage resistance of both sides of the leaking point is directly proportional to the length of pipeline. In this way, the leaking point can be found without inspecting the pipeline with naked eyes.

In conclusion, with the sealing testing device of the present invention, people may break away from the history of the unscientific leakage testing method that the number of drops of the leakage fluid in per unit time and the number of bubbles, or the volume should be distinguished by naked eyes.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings FIGS. 1-3 of the testing device of the present invention, 01 is horizontal plane, 02 a, 02 b and 02 c are rectangular ring seals of final outlet, intermediate outlet and initial outlet of testing pressure, respectively, 03 a is hose assembly, 03 b is piston cylinder seat, 04 is piston cylinder, 05 is piston (assembly), 06 is weight, 07 is height gauge measuring head, 08 refers to timer, 09 is protective support, 10 is overflow groove, 11 is rising ring, 12 is verification container, 31 is fixing screw of piston cylinder seat (03 b).

FIG. 1 is a device for measuring or verifying the leakage resistance of the connection of piston (05) and piston cylinder (04), wherein 05 (piston assembly) is shown in FIG. 4.

FIG. 2 is a device for measuring or verifying the total leakage resistance of the testing system which merely includes the pressure outlet of the piston cylinder (04).

FIG. 3 is a device for measuring or verifying the total leakage resistance of the testing system which includes a pressure output channel formed by 03 a and 03 b.

FIG. 4 shows piston assembly (05), wherein 51 is piston body, 52 is O-shape ring sealing, 53 is sealing cone plug of exhaust vent, 54 is thrust washer of spring (55), 55 is plug-sealing recovery spring, 56 is plug-sealing adjusting screw, 57 is piston mounting screw.

FIG. 5 is a partial view of FIG. 3 where the piston cylinder seat 03 b in FIG. 3 is replaced by the piston cylinder seat 03 b′ having isolating piston 13.

DETAILED DESCRIPTION OF THE INVENTION

The sealing of the normal pressure containers and the systems is to prevent the mutual leakage between the internal fluid and the external atmosphere. The path that causes a mutual leakage of the internal and external fluids is called as leakage path. Each leakage path may have one or a series of seals. The total leakage resistance of all the leakage paths is the sum of the leakage resistances of the serially connected sealing sections. The total leakage resistance of a pressure container or system is the reciprocal of the total leakage derivative, the total leakage derivative is sum of the leakage derivative of each leaking path, and the leakage derivative of each leaking path is the reciprocal of the leakage resistance. Therefore, in order to avoid the intermediate calculation of leakage derivative during some leakage resistance measurements, as shown in FIG. 3, it should be ensured that the total leakage resistance of the testing system which includes the sealing section between the testing fluid pressure generating piston 05 and piston cylinder 04 and the sealing sections 02 a-02 c of the testing pressure channel is far greater than the leakage resistance of the tested pressure container or system.

The means to ensure that the leakage resistance of the sealing section between the piston 05 and the piston cylinder 04 is large enough, first, is to use a series of O-shape ring seals to improve the total leakage resistance, and then is to ensure that the liquid fully fills all the spaces among the O-shape rings to make the O-shape rings work synchronously. For this purpose, liquid should always exist at the piston cylinder port during the assembly operation of the piston 05.

The means to ensure that the leakage resistances of the rectangular ring sealing sections 02 a, 02 b and 02 c including the final outlet, intermediate outlet and initial outlet of the testing pressure is large enough, is to ensure there are sufficiently uniform and sufficient enough plastic deformation in the circumferential direction of the sealing contact surface of the rectangular rings while ensuring that there are sufficiently uniform and sufficient enough elastic deformations in the circumferential direction of the rectangular ring body so that the sealing stress is absolutely greater than the testing pressure. The metal rectangular ring without cold flow can be continuously used in many tests. The polytetrafluoroethylene rectangular ring with cold flow is for disposable use and should be immediately used after the installation, so as to avoid the disappearance of the installation elastic deformation of the rectangular rings due to cold flow, which thus causes the situation that the sealing stress cannot be absolutely greater than the testing pressure.

However, whether the leakage resistance of a leakage resistance testing system is greater or smaller than the leakage resistance of the testing pressure container or system should be proved by measurement or verification. FIG. 1 shows a device for measuring or verifying the leakage resistance of the connection of piston (05) and piston cylinder (04). FIG. 2 shows a device for measuring and verifying the total leakage resistance of the testing system merely including the pressure outlet of piston cylinder (04). FIG. 3 shows a device for measuring or verifying the total leakage resistance of the testing system including a pressure output channel formed by 03 a and 03 b. Actually, expect for the large-scale pressure system having many leakage paths, the leakage resistance of the rest of ordinary pressure containers or systems would not be much smaller than the leakage resistance of the testing device system, and a calculation of intermediate leakage derivative is inevitable. Therefore, the leakage resistance of the leakage resistance testing device system must be stable and reliable, and can withstand verification or reexamination.

An illusion of leakage may appear due to the compressibility of air in a pressure system where liquid is used as the testing fluid, and such phenomenon would affect stability and reliability of the testing. To ensure that the air is fully exhausted from the pressure system, it is preferred to place the testing pressure generating piston cylinder port at the peak point of the pressure system, and install the piston after the testing fluid is slowly filled into the cylinder port. To ensure that the piston 05 can be successfully mounted into the piston cylinder filled with the testing fluid, as shown in FIG. 4, before the assembly operation, the piston mounting screw 57 should be used to push and press against the screw 56 to push the exhaust vent sealing cone plug 53 located at the center of the piston away from the sealing contact position, so that the testing fluid compressed by the installation can be successfully led to the atmosphere. When the last O-shape ring is just mounted into the piston cylinder wall in the assembly, the mounting screw 57 is screwed out so that the sealing cone plug 53 is automatically wedged into the exhaust cone port by the reset structure formed by the washer 54, the spring 55 and the screw 56. To ensure that the leakage resistance of the exhaust vent is infinite, the sealing cone plug 53 should be made of teflon or of metal coated with soft metal or teflon. In order to avoid fake leakage caused by the wedging movement of the sealing cone plug 53, the cone plug and the cone hole should have a sufficient matching length.

When it is inconvenient to place the testing pressure generating piston cylinder port at the peak point of the pressure system to fill the testing fluid, if an isolating piston is added to the pressure channel of the testing device, the testing system and the tested system may be respectively filled with the same or different fluids. When the existing pressure fluid of the tested system is used to test the leakage resistance, an isolating piston should also be added in the pressure channel of the testing device to facilitate the implementation of the leakage resistance measurement. After the isolating piston 13 is added to the piston cylinder seat 03 b shown in FIG. 3, the piston cylinder seat shown in FIG. 3 turn into 03 b′ shown in FIG. 5. The natural limiting end surfaces S1 and S2 of the isolating piston 13 may cause the isolating piston 13 to be unidirectionally compressed. Thus, when the fluid in the tested pressure system is pressurized to an appropriate pressure and thus causes the isolating piston to be pushed to the upper limiting position, after the testing fluid is filled into the testing pressure generating cylinder and the piston 5 is mounted according to the foregoing method, the weight 6 can be added to perform the leakage resistance measurement. The size of the leakage resistance of the isolating piston sealing section only affects the unidirectional pressure-retaining capability of the isolating piston, and does not affect the leakage resistance measurement to be performed.

There is no volume change when the pressure and temperature of the compressed air are not changed. Therefore, under a fixed testing pressure, as long as the testing pressure generating piston has a sufficient movement that meets the requirement of leakage test, the air may also be used as the testing pressure generating fluid, so as to make the test convenient. When the air is used as the testing pressure generating fluid, the liquid resulting in a synchronous deformation of the O-shape rings may be filled among the O-shape sealing rings of the testing pressure generating piston 05. When liquid overflows in the assembly involving the testing pressure generating piston 05, a liquid overflow groove 10 should be attached to the outer surface of the piston cylinder 04 and even a drain pipe should be attached at the bottom of the overflow groove.

The leakage resistance and leakage resistance calculation equation of each standard sealing structure can be determined by using the leakage resistance measuring device, and the leakage resistance R_(L) of the pressure container or system can be calculated according to the standard sealing used and its series-parallel connection. Therefore, on the basis that the leakage resistance R_(L), pressure-retaining capability pt and volume C of the pressure container or system are respectively measured by using the leakage resistance measuring device, pressure-retaining gauge and measurement apparatus, and with reference to the theoretical calculation value, the actual measured value and the equation CR_(L)=pt, the rated volume C, the minimum leakage resistance R_(L) and the minimum pressure-retaining capability pt can be determined. For the stereotypes products with known volume C, leakage resistance R_(L) and pressure-retaining capability pt, merely the pressure-retaining capability gauge is required to test whether the pressure-retaining capability is qualified or degenerated in the factory acceptance and operation monitoring.

When the pressure-retaining capability gauge is used to test the pressure-retaining capability value of a pressure container or system, a double block-and-bleed valve (DBB valve) should be used. The block-and-bleed valve allows its middle channel chamber to communicate with the atmosphere after synchronously cuts off the connection with two pressure containers or systems respectively located at its left and right sides. Therefore, the use of the opening state of the block-and-bleed valve allows the tested pressure container or system to communicate with the pressure fluid or pressure source to obtain the testing pressure. The releasing state of the double block-and-bleed valve is used to implement the pressure-retaining capability test for the pressure container or system. The leakage path that connects the double-and-bleed valve and the atmosphere through middle channel chamber is also a leakage path that blocks the tested container or system. 

What is claimed is:
 1. A sealing tightness measuring device for a pressure system comprising: an assembly comprising a weight, a piston, and a piston cylinder; wherein the weight, the piston, and the piston cylinder are successively arranged through a coaxial plumb bob to produce a fixed testing fluid pressure p against testing fluid inside the piston cylinder communicated with a tested container or system; wherein the sealing tightness is measured by measuring a leakage resistance; the leakage resistance R_(L)=p/I_(L)=pΔt/ΔC, p is the fixed testing fluid pressure of the pressure system, I_(L)=ΔC/Δt is a volume of a testing fluid leaked from the pressure system in per unit time; a ratio of a total gravity G of an assembly of the weight and the piston to a cross-sectional area A of the piston cylinder G/A is the fixed testing fluid pressure p; a product hA of a drop height h of the weight and piston descending along with a leakage and the cross-sectional area A of the piston cylinder is a volume of leaked testing fluid ΔC; and Δt is an elapsed time for the volume of fluid ΔC to leak.
 2. The sealing tightness measuring device for a pressure system according to claim 1, wherein a fixed testing fluid pressure generating assembly is placed or fixed on a horizontal operating platform of a digital display height gauge through a piston cylinder seat; the digital display height gauge is used to measure and display the drop height h of the weight and piston descending along with the leakage; and a separate timer is used to record the elapsed time Δt for the volume of fluid ΔC to leak.
 3. The sealing tightness measuring device for a pressure system according to claim 1, wherein a fixed testing fluid pressure generating assembly is placed or fixed on a horizontal operating platform of a program-controlled detector which can automatically calculate and at least display and print the leakage resistance after automatically collects calculation parameters ΔC and Δt of the leakage resistance, through a piston cylinder seat; and each test is performed under a specified or selected value of p until the leakage reaches a specified or selected value of ΔC or Δt.
 4. The sealing tightness measuring device for a pressure system according to claim 2, wherein the piston cylinder and the piston cylinder seat of the fixed testing fluid pressure generating assembly have an integral structure.
 5. The sealing tightness measuring device for a pressure system according to claim 1, wherein a channel through which the testing fluid pressure passes to the tested pressure system is provided with a pair of isolating pistons and the piston cylinder for isolating the fluid in the sealing tightness measuring device and the tested pressure system.
 6. The sealing tightness measuring device for a pressure system according to claim 1, wherein more than one seal ring is disposed between the piston and the piston cylinder.
 7. The sealing tightness measuring device for a pressure system according to claim 1, wherein an overflow groove is attached on an external surface of the fixed testing fluid pressure generating piston cylinder.
 8. The sealing tightness measuring device for a pressure system according to claim 1 further comprises at least three weight collapsing protective supports.
 9. A pressure-retaining capability measuring gauge for a pressure system, wherein pt=p(p−0.5Δp)Δt/Δp, t is an elapsed time for entire volume of fluid in the pressure system to fully leak out under a fixed pressure p; Δt is an elapsed time for the pressure to drop from p to (p−Δp) caused by a leakage of the pressure system; a value of pt is automatically calculated and displayed after p, Δp and Δt are automatically collected; and each test is performed until the leakage reaches a specified or selected value of Δp or Δt.
 10. The pressure-retaining capability pt measurement gauge for a pressure system according to claim 9, wherein the value of pt is calculated according to (p−0.5Δp)=p.
 11. The sealing tightness measuring device for a pressure system according to claim 3, wherein the piston cylinder and the piston cylinder seat of the fixed testing fluid pressure generating assembly have an integral structure.
 12. The sealing tightness measuring device for a pressure system according to claim 2, wherein a channel through which the testing fluid pressure passes to the tested pressure system is provided with a pair of isolating pistons and the piston cylinder for isolating the fluid in the sealing tightness measuring device and the tested system.
 13. The sealing tightness measuring device for a pressure system according to claim 3, wherein a channel through which the testing fluid pressure passes to the tested pressure system is provided with a pair of isolating pistons and the piston cylinder for isolating the fluid in the sealing tightness measuring device and the tested pressure system.
 14. The sealing tightness measuring device for a pressure system according to claim 4, wherein a channel through which the testing fluid pressure passes to the tested pressure system is provided with a pair of isolating pistons and the piston cylinder for isolating the fluid in the sealing tightness measuring device and the tested pressure system.
 15. The sealing tightness measuring device for a pressure system according to claim 2, wherein more than one seal ring is disposed between the piston and the piston cylinder.
 16. The sealing tightness measuring device for a pressure system according to claim 3, wherein more than one seal ring is disposed between the piston and the piston cylinder.
 17. The sealing tightness measuring device for a pressure system according to claim 4, wherein more than one seal ring is disposed between the piston and the piston cylinder.
 18. The sealing tightness measuring device for a pressure system according to claim 5, wherein more than one seal ring is disposed between the piston and the piston cylinder.
 19. The sealing tightness measuring device for a pressure system according to claim 2, wherein an overflow groove is attached on an external surface of the fixed testing fluid pressure generating piston cylinder.
 20. The sealing tightness measuring device for a pressure system according to claim 4, wherein an overflow groove is attached on an external surface of the fixed testing fluid pressure generating piston cylinder. 